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<h2>Frequently asked questions about LightWAVE</h2>

<h3>What is LightWAVE?</h3>

<p> <b>LightWAVE</b> is a lightweight waveform and annotation viewer and editor.
Use it to view any of the recordings of physiologic signals and time series
in <a href="http://physionet.org/physiobank/database/">PhysioBank</a>, together
with their annotations (event markers).

<p> LightWAVE runs within <a href="browser-compatibility.html">any modern web
browser</a> and does not require installation on the user's computer, tablet, or
phone.  LightWAVE is free software licensed under the <a
href="COPYING.html">GPL</a>.

<p> For more, see the <a href="what-is-lightwave.html">long version of this
answer</a>.

<h3>Why is it called LightWAVE?</h3>

<p> LightWAVE is modelled on WAVE, an X11/XView application I wrote and
maintained between 1989 and 2012.  (WAVE: <em>W</em>aveform and <em>A</em>nnotation <em>V</em>iewer and <em>E</em>ditor.)

<p> It's "light" because you can use it without needing to install it, unlike
<b>WAVE</b>.

<h3>Why was LightWAVE written?</h3>

<p> At one time, WAVE was not difficult to install and run anywhere, because
it's written in portable C, and the libraries that it uses (including X11 and
XView) have been ported to all of the popular platforms (GNU/Linux, Mac OS X,
other Unix-like platforms, and Windows).  XView was abandoned by its authors
years ago, however, and changes in the popular X11 server have resulted in
chronic problems for all applications that rely on XView, including WAVE.
Finding workarounds and patching XView to avoid newly introduced
incompatibilities with updated X11 servers on different platforms has become
increasingly difficult.  WAVE has had a long run and was well liked by those who
used it, but a replacement built on modern standards was clearly needed.

<h3>Why didn't you write LightWAVE in the first place, then?</h3>

<p> WAVE was designed before there were web browsers with fast JavaScript and
SVG engines, mice with scrollwheels, smart phones, touch-input tablets, SVG,
fast and inexpensive high-resolution graphics, JavaScript, Unicode, Wifi,
TCP/IP, 64-bit CPUs in every toaster, the World Wide Web(!), and many of the
user interface elements that are familiar today.  OK, I'm kidding about TCP/IP.

<p> Developing a replacement for WAVE offers the opportunity to revisit
design decisions that would be made differently given current technology.  We
are confident that even WAVE enthusiasts will like LightWAVE.

<h3>How is LightWAVE different from WAVE?</h3>

<p> In terms of function, they are very similar, although LightWAVE is still in
development and lacks some important features of WAVE, notably related to
control of external analysis programs.  These features will appear in LightWAVE
over the next several months.

<p>Architecturally, LightWAVE and WAVE are quite different.  WAVE is a compiled
application that communicates with the user via an X11 server running on the
user's computer.  Usually, WAVE runs on the same computer as the X11 server.
WAVE accesses data, which may be stored locally or on a remote web server such
as PhysioNet, via the WFDB and curl libraries.  Customizing WAVE requires a
good working knowledge of C, X11, XView, and the WFDB library, and a substantial
(though free) software development toolkit.

<p>In contrast, LightWAVE consists of a front end (client) that runs in the
user's web browser, communicating with a pair of back end (server) applications
that run as components of a web server.  Usually, the front end and back end run
on different computers.  The back end accesses data via the WFDB and curl
libraries, in the same way as WAVE does.  Customizing LightWAVE requires only a
text editor.

<h3>What's the magic word?</h3>

<p>See the <a href="http://physionet.org/faq.shtml">PhysioNet FAQ</a>.

<p>George Moody<br>
17 January 2013<br>
(revised 21 April 2013)
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